A mains electricity (AC-powered) device intended to continuously measure the concentration of carbon dioxide (CO2) in a gas mixture through a particular method (e.g., electrochemical, infrared absorption, gas chromatographic, mass spectrometric) to determine a patient's ventilatory, circulatory, or metabolic status. It is typically used to measure end-tidal carbon dioxide (EtCO2) in expiratory gases during the administration of anaesthesia or during bedside monitoring. Commonly known as a capnograph or a capnometer, the sampling method can be "mainstream" and/or "sidestream".